Although glass frits of diverse compositions have been used from before as sealing glass materials, those which, for reduction of environmental load, do not contain a lead component and are of low melting property to enable a firing temperature to be set low to suppress adverse thermal effects on an object to be sealed and an incorporated element thereof, etc., are being regarded as useful in recent years. Tin phosphate-based glass (for example, Patent Literatures 1 and 2) is representative of such low-melting, lead-free glass, and it has also been proposed that its main components of SnO and P2O5 be further added with B2O3 (Patent Literature 3), SiO2 (Patent Literature 4), ZnO (Patent Literature 5), Y2O3 (Patent Literature 6), etc., as a principal component or trace component to improve various glass characteristics, such as sealing strength, glass strength, weather resistance, moisture resistance, durability, etc. However, even though such conventional tin phosphate-based glass frits are low melting, the firing temperature for sealing is still approximately 400 to 480° C. and there is a demand for a glass frit that can be fired at an even lower temperature to improve sealing workability.
SnO—SnF2—P2O5-based glass is known as a lead-free glass of lower melting property that can answer the above demand. For example, in Patent Literature 7 is proposed a tin fluorophosphate material with which, in element ratios, Sn: 20 to 85 weight %, P: 2 to 20 weight %, O: 10 to 30 weight %, F: 10 to 36 weight %, Nb: 0 to 5 weight %, and Sn+P+O+F is 75 weight % or more. Also, in Patent Literature 8 is proposed a tin fluorophosphates material with a glass transition temperature lower than 160° C. and with which, as element ratios, Sn: 55 to 75 weight %, P: 4 to 14 weight %, O: 6 to 24 weight %, F: 4 to 22 weight %, W: 0.4 to 15 weight %.